Field of the Invention
The present invention relates generally to the field of ultrasonic sound generators. More specifically, the present invention discloses a multi-function ultrasonic sound generator with an audio transducer that enables a human operator to hear a frequency-shifted version of the ultrasonic signal.
Statement of the Problem
Ultrasonic sound generators (USGs) producing airborne ultrasound are used for artificially pressurizing with sound waves volumes such as tanks, rooms, automobiles, cabins and enclosures that cannot be pressurized with compressed air or other means for leak testing. One conventional method of use is to place the USG in a room (tank or enclosure), seal it, and from the outside using an ultrasonic leak detector (ULD) try to find where sound is coming through the wall or the seals of the enclosure. The points where this sound is detected are leak points.
Currently some manufacturers offer models that produce a constant sound wave (CW) which when detected by an ultrasonic leak detector or translator sounds like a constant pitch tone. Others produce devices that generate two waveforms, a CW or a burst wave, which is a rhythmic on-and-off cycling of the CW wave. Yet others make simple sweeps that repeat or sweeps that the sound increases in pitch up to a maximum then decreases to a minimum and repeats. With the exception of one device on the market that offers CW and burst wave selectable by the user, all others are either only CW or only sweep.
Conventional USG devices are inaudible when operating and, depending on their sophistication, communicate with the operator via lights (if they are so equipped) to indicate which mode they are in. However since the sound produced by the USG is inaudible, it is typically necessary to use an ULD to verify that the USG is actually producing an ultrasonic signal.
Also, it can be difficult to find an USG that has been placed in a large dark enclosure after the completion of a leak detection job without the use of a ULD, especially if the USG has fallen from its initial position. This is another area in which an audible signal from the USG would be helpful.
Finally, large enclosures such as the hull of a bulk carrier or commercial ship often cannot be adequately covered with one USG, and therefore require multiple USGs placed in different regions within the enclosure. The operation of multiple USGs can cause standing waves especially in symmetrical spaces, which can result in constructive or destructive interference if the devices are tuned to the same frequency. Here also, a need exists for means to enable the operator to verify proper operation and placement of multiple USGs within a large enclosure.
Solution to the Problem
The present invention addresses these shortcomings in the prior art by providing an ultrasonic sound generator that generates both an ultrasonic signal and an audio signal that is replica of the ultrasonic waveform. This enables the operator to verify proper operation and placement of the USG simply by listening to the audio signal before proceeding with ultrasonic leak detection outside the enclosure with an ULD.